1. Field of the Invention
The present invention relates to a relative angle detecting device where difference and sum of received light outputs in light receiving sections divided in two or more are operated, and data regarding a relative position between a light source and a light receiving section are operated, and, for example, a relative position between an input device having the light receiving section and a device body such as a computer or a game device, having the light source is detected and the coordinate input or the like to the device body becomes possible.
2. Prior Art
FIG. 9 shows a remote input device as an example of a device using a relative angle detecting device which uses a light source and a light receiving section and detects a relative position between both sections.
In the remote input device, coordinate information or the like can be inputted from an input device 3 to a screen 1 provided on a device body such as a computer or a game device, and configuration of the remote input device is the same as that disclosed in the specification and drawings of JPA 317479/1993.
In FIG. 9, numeral 1 designates a CRT screen provided on a device body, such as a computer, an AV device, a game device or the like. A light emitting device 2 is fixed on the CRT screen 1, and a light source 2a emitting a reference light is installed to the light emitting device 2.
The input device 3 can be moved freely within a space of a position remote from the screen 1, and a detecting section 4 having structure shown in FIG. 10 is installed on the top end of the input device 3. The detecting section 4 is provided with a reception element 5, and a diaphragm 6 and a visible light cut filter 7 are installed in front of the reception element 5.
If the optical axis orthogonal to the aperture center of the diaphragm 6 is assumed as Z-axis, the Z-axis becomes axis directed along the center of the input device 3 towards the front thereof. As shown in FIG. 11, the reception element 5 is constituted by pin photo diodes having light receiving sections 5a, 5b, 5c, 5d divided in four. Taking the X-Y orthogonal coordinates being orthogonal to the Z-axis, set of the light receiving sections 5a, 5b and set of the light receiving sections 5c, 5dare divided in the Y-axis direction, and set of the light receiving sections 5b, 5d and set of the light receiving sections 5a, 5care divided in the X-axis direction.
The diaphragm 6 has a rectangular aperture, and infrared light emitted from the light source 2a is irradiated as rectangular spot light a to the reception element 5. In respective light receiving sections 5a-5d, a detection current is obtained based on the irradiation area of the spot light .alpha.. Provided that detection outputs based on the irradiation area of the spot light .alpha. in the light receiving sections 5a-5d are Lu, Ru, Ld, Rd respectively, regarding respective detection outputs, difference of received light outputs in set of the light receiving sections divided in the Y-axis direction and difference of received light outputs in set of the light receiving sections divided in the X-axis direction are operated, thereby inclination in the two-dimensional direction (.theta.x, .theta.y) of the Z-axis extending in the front of the input device 3 can be estimated.
Based on the inclination (.theta.x, .theta.y), a cursor mark 8 displayed in the vicinity of the intersection to the Z-axis on the screen 1 is moved on the X-Y coordinates, and the moved amount is transmitted as the X-Y coordinate data or as information data of the inclination (.theta.x, .theta.y), thereby the information data regarding the direction of the input device 3 with respect to the device body are given to the device body. At the side of the device body, the cursor mark 8 is displayed based on the received data and is moved according to the direction of the input device 3. Also drawing to the screen 1 becomes possible.
In a relative angle detecting device used in the remote input device as above described, difference and sum of the received light outputs Lu, Ru, Ld, Rd by the 4-divided light receiving sections 5a, 5b, 5c, 5d shown in FIG. 11 must be estimated, but for the estimation, received light outputs from the 4-divided light receiving sections must be obtained concurrently. Consequently, in each light receiving section, a processing circuit comprising a current/voltage converter, an amplifier, a band pass filter and the like is required.
When the processing circuit is installed separately in each light receiving section, however, if characteristics of the circuit elements constituting respective processing circuits are not coincident, ratio of the received light outputs in respective light receiving sections cannot be obtained correctly. Consequently, electronic parts are selected and circuit adjustment is carried out so that characteristics of the circuit elements installed in respective light receiving sections are coincident. However, the work therefor becomes very difficult, and as a result, it is impossible that characteristics of the respective processing circuits be coincident completely. Consequently, dispersion of the characteristics of the processing circuits is allowed, and corresponding to this, allowable deviation in parts other than the processing circuit becomes strict and therefore the high precision of the device as a whole is inhibited.
Also in various devices obtaining signals by received light outputs of a reception element, in general, a variable gain amplifier for amplifying received light outputs from the reception element is installed, and auto gain control is carried out in that gain of the variable gain amplifier is controlled in response to the intensity of the received light outputs. However, in a relative angle detecting device which must obtain received light outputs different from each other in the intensity always from the light receiving sections 5a, 5b, 5c, 5d shown in FIG. 11, if the amplification gain is controlled in each processing circuit provided in each light receiving section, ratio of the light receiving area in each light receiving section cannot be grasped correctly. Consequently, the gain must be controlled equally to the received light output from each light receiving section, and the circuit configuration for the gain control of the received light output is complicated inevitably.